Transmission of pictures by electricity



May 1, 1928.

1,667,805 H. E. IVES TRANSMISSION OF PICTURES BY ELECTRICITY Filed May 8, 1922 2 Sheets-Sheet 1 May 1, 1928. 1,667,805

H. E. IVES Tiumsmssrou or icTuREs BY swcwmcnv Filed May 1924 2 Sheets-Sheet Mme/22W: flame/ft? [ma Patented May 1, 1928.

UNITED STATES;

PATENT 0FiF C HERBERT E. IVES, or MONTGLAI'R, NEW JEns yjA'ssIGNon ro wEs'rERu ELECTRIC COMPANY, INCORPORATED, oF-NEWi YoRK, N.--Y;,'A conronamoujor NEW YORK.

. TRANSMISSION or PICTURES BXELECTB 'CI'TS C epnnau i jmiiKa e, 1-924. SerialZ No. 71-1 ,7 s5.=

This invention relates to the transmission of pictures by electricity and .more partieu larly to a novel combination off electromag ducing apleasing picture.-.. v

Many attempts have been madeto; transmit pictures by electricity .and n any varieties of equipment l1aye ,.been .,.disclo s ed. Problems of various kinds ha vle arisengln many instances the equipmentemplgyed. not suitable for .useoverlongdistan ce other cases the speed .ottransniissio a, u too slow. In still .othmgcaises the appara-i tns was so. complicatedasg to.-be,:impnae t-icableQ In still other instances-specially constructed transmission lines 2 werei refi q d i n-Y:

An object ofthe ;present invention is to netic and optical devices suitableffor reprq i obviate these difiiculties and 'tOJQCQQI I P l the 7 transmission of pictures; by elect i -ieity in a h y; pma iq lem nnen-z In one embodiment of this Jnventi n, the:

characteristics of -the-..picture-,are traiisr.

mitted as modulations 'fof avoicefrequency. carrier wave, whiclrcan therefore be transmitted over ordinary telephoneline's-(fir.ciu cuits. Such modulated wiive isijimpresseddirectly upon asingle stri-ng lightvalve, the natural frequency of vibration of. the,string being Substantially. tlle same as that of the carrier wave. Bymeans of a simple opticalarrangement controlled bythe light .valve the picture is reproduced in the form of a plurality of parallel lincsrof uniform density and varying Width. This reproduction is peculiarly suitable for making a half; tone zinc or copper plate. v The novel features which are considered characteristic of this invention are set forth with particularity in the; appended claims: The invention both as to -its organization: and method of operation, togeth er gwith other objects and .a(l\-'antages thereof, will;

be explained in the following description, having reference to the accompanying draw-. ing consisting of the following figures:

Fig. 1 is a circuit diagram of asending terminal arrangement for producing .carrier wavemodulat-ed in accordance with the characteristics of the picture to be trans mitted, Fig. 2 is a circuit diagram of a receiving terminal arrangement forreproducing the p cture...

3 diagrammatic showing of the optical system ,of Eig.; 2: (partly in cross section) as viewed from above. 1 Q i; 4 ,F1g. ,%t is aside.yiew of the light valve:

5,6,and] show details-of the light v a lvee. I i l 0t a section the" reproduced -.pi ctiir,e greatly enlarged,

s-3911 a d 11 are v sas ghow the exposureof thereproducedpicture is -effectedppder difierent; conditions. 1

ig; l2 is a, fragmentary showing of the aperture ,torm ng members of the 1 light valve for reference inconnection with the explanation of' F 9, l0 and 11;

c The. same reference characters are used in the seye ral, figures. to indicate :the .same ele- M: 4h 1. Referring now to Fig. 1 a modulatorM is supplied with. ,carrier" waves from a source Cgand. Witl1 picture current from aphotoelectricuc'ell P--and. picture amplifier PA.- Mo'dulated !car'rier waves from :the -inodu-' lato'r. M- are impressed uponthe transmission line L through a 'filter' SPF. The photoelectric :cell :'P is located within a transparent drum 5 which is'driven in any suitable manner by shaft 6. 'Mounted on the-drum fris a transparency f the pictureto be transmitted. .Light from a source 1 8 is focussed by means of lens'9 upon the transparency of the picture through an aperture in'screen 10. The amount of light affecting the. photoelectric cell-P 'is determined by the tone value or density of the elemental area of the transparency? which is at that instant adjacent to the aperture in the screen. 10 at the focal point of the light beam. hTheamount of light within the photoelectric eell Pin turn determines the amount ofcurrent which can flow from the battery--11 through the photoelectric cell P and resistance 12 and consequently,- the potential drop across the resistance 12, which potential .is impressed upon the input cir-' cuit of the picture'amplifier PA. -The aniplified picture current is impressed upon the modulator M' by re'sistance 13 sin'niltaneously with carrier current from the source the lifter RP E are. amplified by amplifier- RA, and impressed by means of transformer 15 on the string 16 o Light. valve Thestring 16 is suspended in a magnetic field and is arranged to vibrate in a direction transverse to the plane of the paper.

Light from the souficeIS is directed" by means of lens 19 upon the conductor-'16.

- The source- 18 is preferablyan incandescent lamp with spiral filament arranged coaxformingelementsof the"valve V are intensely and uniformly illuminated JThe string 1%? is one of these aperture-forming elements; the screen 23, another; andthe' jaws '30 and 31,- the others? The relative location et these members for the n'o cxposure condition is show'nin Fig. 12.

Referring to Fig; 3 fonfiirtherdet'ail's of the optical system, a winding II'is mounted on a hollow central core'o f. amagnetic frame 321'. A magnetic plate '33 connected to'the' frame 32 provides an air-gap in which is located the string' 16 and the other aperture fiormin'g members 30; 31 and 23'. The string 16- is arranged to'vibrate crosswisewithrespect to the andi 31. i l I Referring now to Figs. nto 7 inclusive, which. illustrate the construction of the l'ight valve, the: plate 33 is'connected. to the frame 32 .by means ofakmurled nuts '34, The string v16 is suspended between theterm'ina-l 35 and the post 36' and held at its lower end by the terminal 37. The aperture forming members 30 and. 31 are mountedonflexible studs so that the-:opening'between themmay be adjusted by means of screws 38 and 39. For purposes ofsimplicity this aperture will hereinafter be called the horizontal aperture. while the aperture in member 23 will be called the vertical aperture. The vertical aperture is also adjustable, the ad justment being effected by substituting different screens having different sizes of apertures.

It is seen from F ig. 3 that the light from source 18 passes through the hollow core of -magnetic frame 32. If the string 16 is displaced with respect to the horizontal aperture between members 30 and 31 light will pass through the lens 20 to expose the light sensitive record blank 21 mounted on drum 22 which is rotated by means of shaft 24. The lens 20 is so arranged as to cause animage of the light valve aperture to be formed upon the record blank 21.

The light sensitive surface of the recording blank is such that it is exposed to full aperture between members '30 depth by a single exposure to light from source 18. Additional exposures of the same area have no effect to change its tone value. Thus the developed record possesses only two tone values, one corresponding to exposure and the other corresponding to no exposure.

F or the transmission of pictures the arrangement of Fig. l.' is combined with that of Fig.2 by connecting lines L together by means of a telephone line or circuit. The telephone circuit may be a carrier channel or a radio telephone channel. The drums 5- and' 22 are driven in synch'ronism by any suitable arrangement such, for example,'as that shown in the copending application of M. B. Long Serial N 0.681317, filed December 18, 1923. They are not only rotated in synchronism but are also moved axially relatively to the 'shafis-o and- 24.. As the drum 5 rotates carrier current modulated in accordance with the varyin'a tone values of'thc successive elemental areas of the picture is transmitted over line L and impressed in amplified form upon the string 16 of light valve V. The movement of string 16 relative to the horizontal aperture between members 30 and 31 allows more or less light from the source 18, depending upon the amplitude values of the envelope of the modulated waves, to affect the elemental areas of the light sensitive record blank 21 on the drum 22. The light sensitive record blank 21 is accordingly exposed for the reproduction of the picture in a manner now to be described in connection with Figs. 8 to 12 inelusive.

Fig. 8 shows a portion of the developed picture greatly enlarged. The width of surface exposed during each revolution of the reproducing drum 22 or the width of the trace is represented by the distance 6. This width is determined by the horizontal aperture or the distance between the jaws 30 and 31. Preferably this width b is equal to the axial travel of the drum per revolution. The cross hatched area represents the surface which has been exposed to light from the source 18 due to the vibration of the string 16. Actually this surface is of uniform density. The shape of the boundary line between the exposed and unexposed surfilCQSflYlll be explained hereinafter inconfor-n1, however, a maximum ,exposure results in distinct lines, which form is particularly.

val uable for use; int .thepreparation; ;of zinc oncopper halfton aplates. 5:;Forthis. pre-Y ferredform, theadjustmentzof the system is such ,that. the. string 16 of the light valve: V never;.uncoyers .quite halfzofi the space be. tweenthc jawsl3tland 31.1:

different transmitting speeds is illustrated:

Theq distance .arepresents ,the space along theytracc which isvexpos'eda tvany :grvennn.

stan't and is determined-by the vertical ap i ertu re in anemhen 23. 1: The distance .0 ire-pres sents the distance traveledby; a given'point on the record ;blanl: during .one I cycle. .of the carrier wave and hence during one;complet'e vibration of the string 16 0f the light valve V.; The arrows showthe direction of mo; tion ot'thea'ecorcl.blank relatively to the aperture: forming .members -,of; the plight valve. 2 ill, :1- A

From the foregoing explanatio'n and by reference to. Fig..12, it. is-clear that the solid .curve fiO represents the trace-on. the

record blank of'the movement-of the=point m on the edgeof the string-16 as the string vibrates. Likewise, the-dotted curve-51: represents the trace of the movement o f= point;;

n which is a point on the .same edge 10fthe string- 16, but, on the oppositeedgeofthe' vertical aperture in. member .123. "Each; of:

the other points located between points m and n will trace similar curves. As the ztring it moves downward .in Fig. .12 an area of the record blank will be exposed, one part of which will be defined-bythe edge of jaw 31 and therest-by the movingiedge of the string 16 between the points 171. and n and the edges of the aperture in screen 23. The right sloped crosshatched area 52 1s -ex;

posed during one vibration; the left sloped cross hatched area 53, during the next whration and the vertical cross hatched area 54-. during the third vibra-tion, Succeeding \lllE'illIiUllS are shown in the same manner and may easily be traced.

the jaw- 31.=;Theyareshownimerely fOr pl.lP'-' the; resolution in; the direction; atright: an 7- gles to; this is idetermined by the distance :b.. The effect of .a single sma-ll amplitude vibratiomz. if it 5 occurs {between-two highlyam; plifi'ed Zvibrations; may thus be :entirely .lost;

This Z-is, illustrated .by=..tl ie', righthand 'porthe-iw'ave ipez'ikl 55 :is.- ;enti.1 'elymasked-by. gthe Lnl igs.;9,.l0 and .11 themethodof 'ex-.: posing oneilhalfofea straceiunder variousvalve and. .Za-perture adjustments and i-with exposures; due. -.-to;t-he i wa-gvepeaks e 56 land 51.

In .Fig. 10 ,the speed of 'movement. of the; recordwblank is :the: sam'eias-ine Fig. 9,. but' the exposure a is: ionlyi itworfifth's as ';l arge; g In a this arrangement each iwa-ve =Pfik i performs .its function-and maximumv resolution of the; pictureywith; c0i1tinuity-.:0f-:line' re-s sults. I .fauziiz i -i":$r- .j.=

In Fig. 11 the 'speedof im. vemen'tof'fthe record-blank isidouble: that of Figs/9' and 10. Accordingly, ,onl-yione half cycle of the carrier .wavefioccurs while the record blank movesthrough the-distance a, the resultis that. the exposed areabecomes a. wavy line. If the; speed; iiS "still 2 further; increased, the

- exposed area appearsas' discreet areas.

-As anrexamplejof the-actual values employedain arr arrangement giving a record somewhat like that of Fig. 9, the following valueS-aregivenz- Size of pioture,--5 x7 inches; time of rep'roduct-ion,- minutes; axial travel of drum, 7 inches; axial travel of drum for each revolution,- .02inches; total revolutions for the picture,: 350; circumference of drum 22, 6 inches; linear; travel of recording drum, 2100 inches; linear speed of recording drum, 525 per minute or 8.75" per second; frequency of carrier Wave, 1300 cycles per second; distance a (linear travel per cycle), .00673 inches; distancea (exposure in direction of motion), .02 inches; cycles of carrier wave for exposure a,:2.1.

The actual dimensions of the light valv'e elements (see Fig. 12) are a=.01 b=.01". The exposure on the record blank with the valve wide-open is square 1/50 x 1/50 of air-inch.

In a modification of this arrangement the dimension a (see Fig. 12) is made one half the dimension I), thus a=.005 and b=.01. The exposure on the record blank with the valve wide open will be 1/130 of an inch in the direction of movement and 1/65 of an inch axially. The sizes of these exposures are obtained by means of the optical system including the lens 20.

The damping of the string 16 should be such that "the ainstaamazneousr amplitudes: of vibration will be substantially proportional to the-amplitudes of 't-lr env'el ope 'ofi the inod ula ted carrier waver: criterion: for

" the ramounft or: dampin zis given-in a co- I picture is not only pleasing -in' -='appearance,

but-isin a formusiiita'bl efiorthe reproduction of half tone prints with a mi niinumo'f photographicmanipulationt: I

Whileone embodimentof the invention has been specifically: =deseribedi, the scope o f the invention is to be .liinited onl yby-th'e appended claims.

WhatJis-claimedis: i

i 1.. The ndethod' 0f reproducingza -picture'= which comprises producing a. :carnierwave modulated in'accOrdanQe with the characteristics of the spictuire exposing opposite edges of linearly aligned areazsof a lightsensitive surface =to-awdegree'ipropbrtiozrafl :to= the-am plitucle. of said modhlatted carrier wave, and successively exposirrgli aidgiaentsaguoupse fof linearly aligned"areasto-complete the pic tare. .1. v. 1- s. [i' w.

2. In a system for the transmission of pictu res by electricityg. means to modirla'te a carrier wave inaccordancenwithi the elemental tone values of tl1epictu1'e-,:means :to impress; such modulated-carrier' wave: uporr'a single st 1111;; light. \-'-?ll'\'!'.. said .si'uhrgfnormally -c0mi.; pl-ntely covering an aperture irr saidval've' and vibrating, touncover the aperture-0n either side by an amount direotly proporiional to the amplitude of said modulatedcarrier wave and an optical system controlled by said light valvei'or reproducing lhebic-ture. Y. it

3. In asysteni for the transmission of pie iures by electricity, a-cairrier wave zmodlulated in accordance wvitllth'e elemental tone values of the pictnre,--a moving light sensi-" tive record bl ank, a source of tight for'exposing said record blank, a screen having an aperture: located in the pathot' the lightfrom said source, a. single'movable string adapted when quiescent to prevent exposureofthe record blank bylight from said aperture,

and: aperture-forming: members mounted on said-plana Hi" 5 --5; A. ight valve comprising a. magnetic frame,- a' cent'i al hollow"ma-gnetic core: for saicbtnarnea; magnetizing coi-l surrounding said: core, a: magnetic plate c'onnec table' with said magnetic-frame and forming a concentrated air gap with said' hollow core,'terminall supports mounted-' on said-plate and a conducting member connected between said supports and-adapted to vibrate in said air igapr- 36 A light valve-comprising a: 'magnetic frame;- iar central'l': hollow magnetic core for said: frame, :azrnag'nkaflizing coil surrounding said oore, 'wmaighetic plate connectable with sai'd magnetio fralme a nd' forming a concentrated air.gap with saiid ho llo'w core, ter-- minail supports mountedon said plate, a conducting member connected between said supponts andlcaxrlapted to vibrate in said air gap, a-sorcen having aniaperture-normally registe'ri'ng-witli said c'o'nd'uctin member,- and means to adjust the width 0 said aperture;

Awlight valvecomp-rising a magnetic fraimeg' a'central hollow magnetie core for said frame; ai magnetizing coil surrounding said: core, a -maignetitc :plate' connectable with said-magnetic frame and forming a concentrated: air gap with'said h'ol'lorw core, terminal'supports m-ounted on said plate, a conducting member connected-between said supports and adapted-to vibrate in said air gap, ascreen having an aperture normally regis tering with said conducting member, means to adjust the width of'said' aperture, and a second-screenhaiving an aperture variable in the direction of the length of the vibrating conducting member.

8. A light valve coin-prising a magnetic circuit including an; air gap, aconductor lo cated in said 'ai-r gap and arranged to move when current'flbws therethrough, and an adjustable member forming with said conductor a variable aperture for a given value of current.

In witness whereof, I hereunto subscribe my name this 7 day of May, A. D. 1924.

HERBERT E. IVE'S. 

